It is known in the prior art that organo phosphoric acids form self-assembled monolayers (SAMs) on metallic substrates. The substrates should have on their surfaces some oxide and/or hydroxyl groups. It is believed the acid groups covalently bond to the surface of the metal substrate by reaction with the oxide or hydroxyl groups and the organo groups spontaneously arrange themselves in an ordered array extending in a somewhat perpendicular direction from the substrate with the organo groups being substantially parallel to one another. The resulting film or layer is of a monolayer configuration and, although extremely thin, the SAMs have strong adhesion to the metal substrate because of the covalent bonding; and, because of the well-ordered orientation of the organo groups, the SAMs significantly affect the surface properties of the metal substrates.
However, if the surface of the metal substrate is contaminated such as with processing oils, dust or grit, the ability of the organo phosphorus acids to covalently bond to the metal oxide and/or hydroxyl groups may be compromised and SAMs will not spontaneously form or will form in a discontinuous manner leaving gaps in coverage and poor surface properties. Typically, the metal substrate will be rinsed with an organic solvent to clean the substrate; however, this is insufficient to remove all the surface contaminants and to provide sufficient metal oxide and/or hydroxyl groups so as to provide for the formation of dense SAMs. Also, treatment with caustic solutions tends to etch the protective oxide layer from the surface of the metal and creates a surface that must be further modified to reform the oxide layer.